Heavy Metal Concentrations in Fish from Oguta Lake: Exceedances of Permissible Limits and Public Health Concerns

Abstract: This study investigated the concentrations of heavy metals—mercury (Hg), lead (Pb), cadmium (Cd), iron (Fe), and copper (Cu)—in five fish species (African Sharptooth Catfish, Mud Fish, Hong Kong Tilapia Fish, and Knife Fish) from Oguta Lake, Owerri, Imo State, Nigeria. The specific objectives were to (1) assess heavy metal concentrations in fish organs (muscle, liver, gills) obtained fom Oguta lakes, (2) compare contamination levels across species, and (3) evaluate potential health risks associated with fish consumption. A stratified random sampling technique was used to collect fish samples, and heavy metal analysis was conducted using Atomic Absorption Spectroscopy (AAS). Data were statistically analyzed using SPSS (version 25.0), with significance set at p < 0.05. The results revealed alarming heavy metal contamination, with concentrations exceeding FAO/WHO permissible limits in most cases. Mercury (Hg) was highest in the liver of African Sharptooth Catfish (2.569 mg/kg; limit: 0.5 mg/kg), while cadmium (Cd) peaked in the same species’ liver (54.757 mg/kg; limit: 0.1 mg/kg). Lead (Pb) was most concentrated in the muscle of Hong Kong Tilapia Fish (35.882 mg/kg; limit: 0.3 mg/kg), and iron (Fe) levels were highest in the liver of Mud Fish (103.306 mg/kg; limit: 40 mg/kg). Copper (Cu) showed relatively lower contamination, with a maximum of 2.361 mg/kg in Knife Fish gills (limit: 3 mg/kg). Statistical analysis indicated no significant differences (p > 0.05) in metal concentrations across species, except for mercury (F-value = 3.444, p = 0.035). These findings highlight severe pollution of public health concerns in Oguta Lake, due to environmental contamination, industrial effluents discharge, agricultural runoff, and improper waste disposal. Chronic exposure to such heavy metals through fish consumption poses serious health risks, including neurotoxicity, kidney damage, and carcinogenic effects.